Field of the Invention
The present invention relates to a measurement apparatus.
Description of the Related Art
In order to analyze the base sequence of DNA (deoxyribonucleic acid), RNA (ribonucleic acid), or the like, a base sequence analyzing apparatus (sequencer) is employed. As a next-generation (fourth-generation) sequencer, various kinds of techniques have been sought by research institutions and industries. As one of such prospective techniques, the gating nanopore sequencing technique has attracted attention.
With the gating nanopore sequencing technique, DNA or RNA is moved such that it passes through a gap between a pair of nanometer-order electrodes (nano-electrodes). The tunnel current that flows through the electrode gap changes according to the base type (A, G, T, C) that passes through the electrode gap. The base sequence is determined based on the change in the tunnel current. This technique is anticipated to have the potential to provide a very low-cost and very compact-size apparatus that is capable of analyzing a base sequence. It should be noted that, in the present specification, examples of such a “nano-electrode” include sub-micro electrodes and micro electrodes having a larger size.
Also, as a method using a tunnel current in the same way as with the gating nanopore sequencing technique, the MCBJ (Mechanically Controllable Break Junction) method has been developed. With the MCBJ method, a nano-electrode is formed by breaking a metal wire.
As an important element technology, such a sequencer requires a current measurement device that is capable of measuring a tunnel current that flows through a nano-electrode gap with sufficiently high precision. That is to say, such a tunnel current has a current value on the order of several tens of picoampere (pA). Accordingly, in order to judge the base type, there is a need to detect a difference in conductance on the order of several picoseconds (ps).